This invention relates to improved dehydrated potato granules and to a process for the preparation of these granules.
The process now generally in use for the production of pre-cooked dehydrated potato pieces is commonly referred to as the "add-back" process. This name derives from the main distinguishing feature of the process which is that a large proportion of the final dried potato product is recycled and mash-mixed with freshly cooked potatoes. Various subsidiary steps, each essential to the particular process, as, for example, pre-cooling or conditioning, may intervene at one point or another. At any rate, the recycling and mash-mix technique serves to reduce the moisture content of the mixture down to about 35% and to subdivide the cooked potato tissue into fine granules. The mixture is subsequently dried in dryers which might typically consist of an air-lift dryer and/or fluidized bed dryer.
In the above described processes, about 85-90% of the dried product is required to be "added-back" for mixing with freshly cooked potatoes. Hence, only 10-15% of the total process throughput is packed as a final product.
"Add-back" processes are marked by a number of distinct disadvantages. Perhaps the most obvious of these is that, due to the high recycle rate, the processing equipment is required to be, relatively very large. In addition, any given quantity of potatoes passing through the system is subjected to mash-mixing, conditioning, final granulation and any other operations which may be present in the system, on an average of 6-10 times before packing. This also is a direct result of the high recycle rate. These repetitive treatments may result in cell damage due both to mechanical breakage and to repeated exposure to high temperature. Common manifestations of such damage are that the reconstituted product may have an undesirable gluey texture and a scorched or burnt flavour, and be of reduced nutritional value particularly with respect to more heat sensitive components, in particular ascorbic acid (Vitamin C).
A further troublesome problem stemming from high recycle rate is that a batch of potatoes that was defective before entering the process, or a quantity that was rendered defective by poor control, etc., will continue to contaminate new batches for a lengthy period. Associated with this problem is that of build up, where the high amount of recycle can result in the creation of concentrations of undesirable elements, for example, bacteria.
In addition to problems associated with recycle, "add-back" processes often involve a conditioning step following mix-mashing wherein the potato is subjected to a lengthy tempering period at a temperature such that microorganism activity and/or undesirable chemical reactions may occur resulting in such problems as discoloration.
With so many problems inherent in these systems, attempts have been made to devise processes which would improve the processing technique by employing a straight-through method with the elimination of recycling. Various systems have been proposed each with its distinguishing characteristics and also with a number of common features. Obviously, all will require steps such as cooking, drying and mashing. However, the arrangement of the common steps, the addition of new ones, the deletion of unwanted ones and the conditions under which each step is carried out, all serve to clearly set off each process from the others. In each case a new process is designed to improve the efficiency of operation while maintaining or improving the desirable characteristics of the product. On the other hand, each process proposed to date exhibits one or more undesirable characteristics, for example, in its effect on the physical or nutritional qualities of the product.